The use of vascular grafts for bypassing peripheral vascular occlusive conditions is believed to be well known, as is the use of microporous expanded polytetrafluoroethylene (ePTFE) in prosthetic vascular grafts. U.S. Pat. No. 6,436,135 to Goldfarb shows and describes an ePTFE prosthetic vascular graft; U.S. Pat. No. 6,273,912 to Scholz et al. shows and describes a flanged graft for end-to-side anastomosis; U.S. Pat. No. 6,190,590 to Randall et al. shows and describes an apparatus and method for making flanged grafts for end-to-side anastomosis; and the publication entitled, “Venaflo™ Vascular Grafts, Information for Use” shows an ePTFE graft with a modified venous end, each of which is incorporated by reference into this application as if fully set forth herein.
In current clinical practice, a peripheral anastomosis between a bypass prosthesis and a peripheral artery has been performed by either direct anastomosis, interposition of a venous segment at the anastomotic site, anastomosing the prosthesis with a long venous patch sutured into the artery, enlargement of the prosthesis with the anastomotic region using a venous patch, or interposition of a venous cylinder between the prosthesis and the artery. In bypass grafting, it is believed that hemodynamic factors are a major cause of thrombosis and the development of subintimal hyperplasia at the anastomotic site. In particular, hemodynamic phenomena may induce the development of intimal hyperplasia, e.g., occlusive legions that are predominately located at a venous anastomosis, which is believed to adversely affect the longevity of ePTFE grafts. Disturbed flow patterns, e.g., recirculation zones, flow separation and reattachment, development of stagnation points, and the rate of change of shear stress can be amplified due to abnormally high flow rates present in arteriovenous grafts. In the paper entitled “The Importance of Correct Trimming of Venaflo Graft Proven by CFD,” presented at the 4th International Congress of the Vascular Access Society, May 25th to 27, 2005, Berlin, Germany, which is hereby incorporated by reference into this application, Dr. Ulf Krueger describes how graft geometry at the site of a venous anastomosis directly affects hemodynamic factors.
In order to mitigate intimal hyperplasia in an arteriovenous graft, it is known to use a bulb-like shape of the venous end-to-side anastomosis. Preferably, this includes a prefabricated cuff, which is attached to the venous anastomosis, resulting in an enlargement of anastomotic room with a curved vein floor. Flow studies related to the known vascular grafts are believed to suggest that blood flow patterns are optimized compared with previously known non-vascular grafts. However, the positive properties are closely connected with the correct design of the venous anastomosis. The hemodynamic is determined by the anastomotic metrics. Hence, the size and shape of the cuff must closely match the vein diameter in order to realize the aforementioned benefits. The prefabricated cuff, according to the known device, is only roughcast and may be trimmed relative to the vein diameter at maximal dilation by a clinician during surgery. However, if a graft is not trimmed precisely, sub-optimal results may occur.
Leonard Pinchuk, et al., U.S. Pat. No. 4,872,455 (Oct. 10, 1989), shows an anastomosis trimming device that is used for trimming a section of a tubular structure, such as a blood vessel or vascular graft, which is to be anastomosed, to provide an anastomotic end with a smooth, reproducible shape. That is, Pinchuk shows and describes a tool to specifically cut a middle or tubular portion of a graft instead of a flanged or cuffed end of a vascular graft.
Applicants have recognized that precise trimming of a prefabricated flanged end or cuff to achieve optimal blood flow patterns through the cuff can be accomplished through detailed instructions, including trim lines disposed on the cuff and/or through the use of tailoring devices.